1. Field of the Invention
The present invention generally relates to alarm systems and, more particularly, to a multi-zone alarm system for, and method of, protecting a premises from alarm events such as burglary and fire.
2. Description of the Prior Art
Conventional alarm systems have not proven to be altogether satisfactory in preventing unauthorized entry and/or in preventing fire damage to industrial and/or home premises. With the evergrowing sophistication of the intruder or arsonist, conventional alarm systems are easily compromised by short- or open-circuiting the individual alarm sensor devices.
In a typical conventional alarm system installation, a plurality of burglary-type sensors are mounted in one closed circuit loop, and a plurality of fire-type sensors are mounted in another closed circuit loop. However, the burglary sensors are all of the same type, generally series-connected normally-closed switches each having two contacts. The fire sensors are likewise all of the same type, generally parallel-connected normally-open switches each having two contacts. Each loop has its own alarm sensing element for detecting whether a burglary sensor or a fire sensor has been actuated.
In order to overcome the increasing expertise of the intruder/arsonist, more sophisticated burglary and fire sensors, such as infrared light, ultrasonic sound, microwave, have been developed. These sophisticated sensors are switches having a three-contact configuration. One contact is a common contact, and defines a normally-closed branch path with a second contact, and defines a normally-open branch path with a third contact. However, in order to install these multiple contact sensors into an existing two-wire loop, adaptors for converting a three-contact switch to a two-contact switch are needed.
The above-described installation techniques suffer from many disadvantages. First of all, it is easy to compromise the burglary sensors by simply jumping its respective two contacts. The fire sensors are easily compromised by cutting the conductors leading to its respective two contacts. A combination fire-burglary system requires two loops, two sensing elements, and extra wiring. This represents additional costs not only in duplication of parts, but also in terms of the labor required to install the extra loops around a premises. Moreover, the extra wiring increases the probability of accidental breaks, thereby leading to inadvertent tripping of the alarm by the user of the premises. Still further, the sophisticated multiple contact sensors cannot be inexpensively installed, because they require additional wiring and expensive adaptors.